1. Field of the Invention
The present invention relates to the preparation of alumina, at least a portion of which comprising ultrafine boehmite, and to a variety of useful final products comprised thereof.
2. Description of the Prior Art
It is known to this art, from French Pat. No. 1,261,182, to prepare ultrafine boehmite from aqueous dispersions of alumina by heating same in the presence of a strong, monobasic acid. One of the principal disadvantages of this process consists of the fact that it is necessary to utilize as the source of alumina products such as aluminum chloride, or nitrate solutions obtained from metallic aluminum, which are difficult and expensive to produce.
And in French Pat. No. 1,381,282 there is described a process for the preparation of ultrafine alumina which consists of treating, at a temperature of between 60.degree. and 150.degree. C., a suspension or a cake of amorphous, hydrated alumina gel obtained generally by the continuous precipitation of a solution of sodium aluminate in nitric acid. This process requires the employment, as starting material, of a cake of alumina gel which is rather delicate to prepare, requiring numerous stages therefor (precipitation, filtration, washing, drying, etc.).